Polyandry, multiple mating and sexual conflict in a water strider, Aquarius paludum

Sexual selection results from competition between individuals over access to gametes of the opposite sex. Starting with anisogamy, with females producing larger and fewer gametes than males, females usually invest more in reproduction and thus have lower potential reproductive rates than males. Therefore males are traditionally suggested to compete over females whereas females are choosy. The different evolutionary interests between the sexes result in different selection regimes considering e.g. mating rates. In some species, this conflict is even seen as apparent struggles between males and females over mating decision and/or duration, resulting in antagonistic coevolution with both sexes evolving adaptations to gain more control over the other sex. In this thesis, I studied the role of A. paludum female abdominal spines as an adaptation to reject male mating attempts. I studied both the effect of polyandry and multiple matings on female fecundity to distinguish between the potential material and genetic benefits from mating to females. I also explored the role of various male and female morphological traits on precopulatory sexual selection and the consequent female reproductive output. My results show that female abdominal spines are likely evolved through arms races between the sexes to increase female control over mating decision but according to my studies, female spines are not under active selection. Instead, certain male morphological types were more successful in achieving matings, and mating with these males also increased female fecundity. I found that multiple matings increase female fecundity up to a point, supporting a theory of optimal female mating rate. According to my results, the benefits from multiple mating to A. paludum females result from material origin whereas polyandry per se is even detrimental to female fecundity.